Clinically significant alloimmunization to red cell antigens occurred in 28 percent of transfused patients in a sickle cell clinic. Therefore, a prospective study was undertaken to determine whether matching donors carefully for 17 blood group antigens would diminish the risk of further alloimmunization in patients on a chronic transfusion program. Alloantibodies had developed previously in 8 of the 12 patients. After chronic transfusion with selected donors, four new antibodies developed in three patients. Three antibodies were due to errors in phenotyping or matching, and one was due to an antigen that was not tested for in the protocol. The incidence of developing antibodies per unit transfused was diminished tenfold when selected donors were used. Autoantibodies developed in five patients (42%), but these did not seriously interfere with the transfusion therapy. It was concluded that matching for red cell antigens may diminish the incidence of alloimmunization in patients with sickle cell anemia requiring transfusion.

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Suspensions of murine bone marrow cells were stained with acridine orange (A-O) and observed under fluorescent microscopy after treatment with various injurious agents in order to establish the staining characteristics of "live" and "dead" cells. The percentage of viable cells demonstrated by the "A-O viability test" were correlated with eosin and trypan blue dye exclusion and tissue culture transformation viability tests. In general, the A-O test demonstrated the viability of cells preserved by freezing as effectively as the other in vitro tests. In addition, the A-O test may be more sensitive in determining the viability of cells where metabolic processes have been injured by poisons or change in pH.

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